1. Field of the Invention
The present invention relates to circuit modules and composite circuit modules, and, more particularly, to a circuit module and a composite circuit module provided with a surface acoustic wave filter including a piezoelectric element.
2. Description of the Related Art
Examples of a circuit module in the related art include an electronic component apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2002-299996. FIG. 9 is a cross-sectional view of an electronic component apparatus 500 disclosed in Japanese Unexamined Patent Application Publication No. 2002-299996.
The electronic component apparatus 500 includes a SAW device 502 and a base 504. The SAW device 502 includes a piezoelectric monocrystal substrate 506 and a substantially comb-shaped electrode 508. The substantially comb-shaped electrode 508 is disposed on the piezoelectric monocrystal substrate 506. The SAW device 502 is disposed on the base 504 via bumps so that the substantially comb-shaped electrode 508 faces the base 504. The electronic component apparatus 500 having the above-described structure is mounted on, for example, a motherboard when being used.
When the electronic component apparatus 500 is heated and cooled in a reflowing process, a connection in the electronic component apparatus 500 may be broken. More specifically, the piezoelectric monocrystal substrate 506 in the electronic component apparatus 500 is made of, for example, lithium tantalite. The base 504 is made of, for example, ceramics such as alumina. A motherboard is made of, for example, glass epoxy. Lithium tantalite, alumina, and glass epoxy have different material properties such as a coefficient of linear expansion and a Young's modulus. Accordingly, when the electronic component apparatus 500 is heated and cooled in a reflowing process, the SAW device 502, the base 504, and a motherboard are deformed in different ways. As a result, in the electronic component apparatus 500, a connection may be broken. The inventor of the invention described and claimed in the present application discovered via computer simulation that the connection between the SAW device 502 and the base 504 is easily broken.